【判断题】采用标准加入法可以提高分析方法的灵敏度。
【单选题】实体完整性要求主属性不能取空值,这通常是通过( )。
【单选题】实体完整性要求主属性不能为空值,这一点可以通过( )来保证。
【单选题】实体完整性规则要求主属性不能取空值,为此,可通过______来保证。
【单选题】The digging will seem easier if you divide up the garden by marking_________small sections with your spade. [ ]
【简答题】Part IV 选词填空 Good communication is the key to success when learning online. You should take the opportunity to get to know your teacher and classmates through email and by (26) _______ in Internet dis...